Sharpening images for the web has been troublesome since the invention of the internet. Artifacts come out of no where, colors morph and change your image to a toxic dump site. With a few basic steps you can master the sharpening process and get accurate colors! The following tutorial takes place in Photoshop CC but it's the same process for earlier versions of photoshop. Resizing the image size is the first step in creating the perfect web image. Often if you are editing your image in photoshop your DPI is probably somewhere around 300. To resize head over to >image >image size. you can also use the keyboard shortcut alt+ctrl +i. This is what it looks like.
From here the first thing I do is lower the resolution to 72 pixels/inch. This will lower your width and height accordingly. From here it's a matter of what size you want to make your image. For facebook I recommend a width of 843 pixels/inch. If you change one dimension the other will adjust automatically. If you're posting to your website or other social media. A quick google search will aid you in correct sizing in terms of pixel width and height. It is very important to resize your image before sharpening. Otherwise you will have mad artifacts! See image below for the settings I have changed.
Press OK. Now head up to the menu >view>100%. Now we can sharpen. There are about 3.4 million ways to sharpen so if you have a preferred method, now is the time to implement it. This is how I sharpen my web images.
Create a new background layer using cmd on mac or ctrl on pc + J. Directly above your new layer you will see the blending modes, it should be on normal. Click on the drop box and change it from normal to overlay. Now it will look a bit funky but don't worry, that's supposed to happen. From here head to the menu >Filter>Other>High Pass. Once you select High Pass, a box will open up with a radius slider. Your image should also look a bit more normal! Simply move the slider back and forth until your image looks sharp and press ok. Tada! Now you have a sharp image. The rest is easy.
Now head up to >file>save for web and devices. A box will open up looking like this.
If you look at the image above those are the settings I use. The most important thing is to make sure you check the convert to sRGB box. You can also play with the quality slider. I normally keep mine at 100, but you can play with it. In some cases you can take the quality down to 60 without any noticeable image changes. It will make your image size smaller if that is a desired effect.
From here you press save, pick a location for your image, and you're done. Now you will have the perfect sharpened image for the web! The final sharpened image is below!